Filtering cytokines??

Im treating my cells with recombinant cytokines, the cytokines were made up a good while ago in the lab and I am wondering can I make them up in media (from the stock conc) and then filter it before adding it to my cells to ensure it's totally sterile or will this remove my cytokines? As we are not sure if they got opened so might not be sterile anymore... it's been a while since anyone used it Or any idea how to check it is contamination free? Any help would be great before I have to treat them

I wouldn't recommend added the cytokine to the main media bottle before filtering. You may loose some of the cytokine by filtering but more importantly, you may loose activity if the cytokine is diluted for too long a period of time.

If you are only adding the cytokine to your cells for up to 48h, it is not crucial that it be 100% sterile. Most cytokines come "clean" but never 100% sterile to begin with.

I'm treating my cells for 5 days... I add the cytokine to the media on the day of use and I was going to filter this before adding it to the cells-rather than adding it to the whole bottle.
If there is contaimination should I be able to see it under the microscope? Just in the cytokine placed in a petri?